A quinoline small molecule blended modified polymer dielectric material and a preparation method and application thereof

Abstract

The application discloses a quinoline small molecule blended modified polymer dielectric material and a preparation method and application thereof, and belongs to the technical field of capacitor films. The preparation raw materials comprise quinoline derivatives, polymethyl methacrylate, styrene-methyl methacrylate copolymer, polyetherimide, polypropylene and N-methyl pyrrolidone solution, and the preparation steps comprise blending and film preparation. The blending solution or eutectic mixture is prepared through blending, and the polymer dielectric film is prepared through a flow casting method or bidirectional stretching. The prepared quinoline small molecule blended modified polymer dielectric film has excellent electrical properties, can reduce the leakage current of the polymer material, has high DC breakdown field strength, high energy storage density and low energy loss, and is easy to realize large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thin film capacitor preparation, and particularly relates to a quinoline small molecule blended modified polymer dielectric material, a preparation method and application thereof. BACKGROUND

[0002] The dielectric capacitor has the advantages of super-high power density, extremely low loss and higher working voltage, and thus is not only an important basic electronic component, but also plays a major role in bypass, decoupling, filtering and energy storage in circuits, and is widely used in electronic power systems, energy systems and cutting-edge weapon systems. The dielectric capacitor can be mainly divided into three types according to the dielectric material used, namely organic polymer dielectric capacitor, inorganic dielectric capacitor and electrolytic capacitor. Among them, the capacitor with organic polymer as dielectric material, i.e. organic thin film capacitor, has been widely used in electric vehicles, wind power, photovoltaic, lighting and railway locomotive industries due to its light weight, good processing performance, low production cost, high dielectric strength, good self-healing property, simple integrated assembly process and no liquid medium. The currently commercially available polymer dielectric material is biaxially oriented polypropylene (BOPP), which has the advantages of high voltage resistance, low loss, self-healing, good stability and the like. With the development trend of miniaturization of electronic power systems, the energy storage density of 2-3 J / cc of BOPP cannot meet the demand. Therefore, it is urgent to modify BOPP or develop new polymer-based dielectric materials to achieve high energy storage density and low loss.

[0003] From the formula U e = 0.5ε0ε r E b 2 It can be seen that the energy storage density (U e ) of the dielectric material is determined by the dielectric constant (ε r ) and the breakdown field strength (E b ). To improve the U e of the polymer thin film capacitor, its ε r and E b need to be improved. For BOPP, the internal molecular structure determines its low dielectric constant (~2.2). In order to improve the ε r , polar groups can be introduced into BOPP through copolymerization or blending modification to improve its dielectric constant. Chung TC et al. introduced a certain amount of polar groups (such as -OH, -NH2, etc.) into PP, so that the ε r can be improved to 4, and the U e can reach 7.0 J / cm 3 . However, the introduction of polar groups also leads to high relaxation loss and low release efficiency.

[0004] Based on the above analysis, the polymer-based dielectric material realizes high energy storage density and low loss at the same time, which strongly depends on high breakdown field strength. At present, the BOPP film E b is produced by using imported raw materials and imported double-pulling line in China. The breakdown field strength of the BOPP film E is about 600-650 MV / m, but its energy storage density is still difficult to meet the requirement of high energy storage density. The linear dielectric such as polymethyl methacrylate and polyetherimide with high temperature resistance is expected to realize high energy storage density and low loss, but its breakdown field strength of only 500 MV / m also limits its application. Therefore, on the basis of not sacrificing the releasable efficiency, it is urgent to develop a method for improving the breakdown strength of the linear dielectric such as BOPP, PMMA and PEI. SUMMARY

[0005] The purpose of the present application is to solve the above problems, and a series of quinoline small molecule blended modified polymer dielectric materials are designed. The specific design scheme is as follows:

[0006] A preparation method of a quinoline small molecule blended modified polymer dielectric material, comprising the following steps:

[0007] (1) blending to prepare a blend solution or a eutectic mixture:

[0008] The polymethyl methacrylate, styrene-methyl methacrylate copolymer and polyetherimide are added into the N-methyl pyrrolidone solution, and the quinoline small molecule is added to obtain a blend solution; or the quinoline small molecule and the polypropylene are melt blended to obtain a eutectic mixture;

[0009] (2) preparing a film:

[0010] The blend solution is cast on a substrate, and is first dried at a temperature lower than 100 DEG C, and then is dried by heating, and is naturally cooled and immersed in water for peeling to prepare a composite wet film; or the eutectic mixture is cooled, granulated, extruded and shaped, and then is biaxially stretched to prepare a blend film.

[0011] Preferably, in step (1), the mass fraction ratio of the quinoline small molecule to the polymethyl methacrylate, the styrene-methyl methacrylate copolymer, the polyetherimide or the polypropylene is (0.01%-8%):(99.9%-92%).

[0012] Preferably, in step (1), the mass fraction ratio of the polymethyl methacrylate, the styrene-methyl methacrylate copolymer and the polyetherimide to the N-methyl pyrrolidone solution is 30%:70%.

[0013] Preferably, in step (1), the temperature for melt blending is 170 DEG C-200 DEG C.

[0014] Preferably, in step (2), the preliminary drying temperature is 60 DEG C, and the preliminary drying time is 4h.

[0015] Preferably, in step (2), the temperature rising drying time is 6h; the temperature rising drying temperature of the solution of the blend of polymethyl methacrylate or styrene-methyl methacrylate copolymer is 150℃; and the temperature rising drying temperature of the solution of the blend of polyetherimide is 250℃.

[0016] The application further provides the quinoline small molecule blend modified polymer dielectric material prepared by the preparation method.

[0017] The application further provides application of the quinoline small molecule in the blend modified polymer dielectric material.

[0018] The application further provides application of the quinoline small molecule blend modified polymer dielectric material prepared by the preparation method in a dielectric capacitor.

[0019] Compared with the prior art, the application has the beneficial effects that:

[0020] 1. By introducing the electron-deficient quinoline small molecule with good compatibility and thermal stability into the dielectric polymer with high glass transition temperature (the intramolecular carbon-nitrogen double bond in the skeleton of the quinoline small molecule makes it in an electron-deficient state, and the quinoline small molecule has very high electron affinity), the carrier migration is effectively inhibited, the electrical conduction loss of the polymer material is greatly reduced, the generation of Joule heat is reduced, and the polymer dielectric material with extremely high energy storage density is obtained.

[0021] 2. The quinoline small molecule has extremely high electron affinity, can capture high-energy electrons, weaken the impact of electrons on the polymer molecular chain under a strong electric field, and greatly improve the breakdown field strength of the polymer material.

[0022] 3. The polymer dielectric material has low price, simple preparation method, good dielectric energy storage performance, can be made into a large-area, high-quality, dielectric performance uniform thin film, and is easy to realize large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application, in which:

[0024] Figure 1 is the energy level structure change formed in the polymer material described in the application;

[0025] Figure 2 is the molecular structure diagram of the four polymer matrices in the application, in which:

[0026] Figure 2 a is polymethyl methacrylate, Figure 2 b is styrene-methyl methacrylate copolymer,Figure 2 c is polyetherimide, Figure 2 d is polypropylene;

[0027] Figure 3 are five different quinoline small molecule structures exemplified in the present invention, wherein:

[0028] Figure 3 a is 8-hydroxyquinoline, Figure 3 b is quinoline-3-carboxaldehyde, Figure 3 c is 6-fluoro-2-methylquinoline, Figure 3 d is 2-cyclopropyl-4-(4-fluorophenyl)quinoline-3-carboxaldehyde, Figure 3 e is 8-fluoroquinoline;

[0029] Figure 4 is a Weibull distribution plot of breakdown field strength of the 8-hydroxyquinoline blended modified polymethyl methacrylate material provided in the present invention;

[0030] Figure 5 is a plot of the change of energy storage density and discharge efficiency with electric field strength of the 8-hydroxyquinoline blended modified polymethyl methacrylate material provided in the present invention;

[0031] Figure 6 is a Weibull distribution plot of breakdown field strength of the quinoline-3-carboxaldehyde blended modified styrene-methyl methacrylate copolymer material provided in the present invention;

[0032] Figure 7 is a plot of the change of energy storage density and discharge efficiency with electric field strength of the quinoline-3-carboxaldehyde blended modified styrene-methyl methacrylate copolymer material provided in the present invention;

[0033] Figure 8 is a Weibull distribution plot of breakdown field strength of the 6-fluoro-2-methylquinoline blended modified polyetherimide material provided in the present invention;

[0034] Figure 9 is a plot of the change of energy storage density and discharge efficiency with electric field strength of the 6-fluoro-2-methylquinoline blended modified polyetherimide material provided in the present invention;

[0035] Figure 10 is a Weibull distribution plot of breakdown field strength of the 8-fluoroquinoline blended modified polypropylene material provided in the present invention;

[0036] Figure 11 is a plot of the change of energy storage density and discharge efficiency with electric field strength of the 8-fluoroquinoline blended modified polypropylene material provided in the present invention. DETAILED DESCRIPTION

[0037] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplifying the present application, the components and arrangements of the specific examples are described in the following. Of course, they are only examples and are not intended to limit the present application. In addition, the present application can repeatedly refer to the same reference numerals and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or arrangements discussed.

[0038] Embodiments

[0039] A quinoline small molecule modified polymer dielectric material and a preparation method thereof, the preparation raw materials include quinoline small molecules, polymethyl methacrylate, polyetherimide, styrene-methyl methacrylate copolymer, polypropylene, N-methyl pyrrolidone solution, the preparation steps include mixing step and film preparation step, the mixing step is to obtain a mixed solution or a eutectic, and the film preparation step is to obtain a mixed film by using spin coating, casting and melt extrusion biaxial stretching.

[0040] (1) Mixing:

[0041] In the mixing step, for polymethyl methacrylate, styrene-methyl methacrylate copolymer, polyetherimide, first add polymethyl methacrylate or styrene-methyl methacrylate copolymer or polyetherimide into N-methyl pyrrolidone solution to obtain a polymer solution, then independently add 8-hydroxyquinoline, quinoline-3-carboxaldehyde, 6-fluoro-2-methylquinoline, 2-cyclopropyl-4-(4-fluorophenyl) quinoline-3-carboxaldehyde or 8-fluoroquinoline and other quinoline small molecules to obtain a mixed solution; for the polypropylene matrix, add polypropylene and 8-hydroxyquinoline, quinoline-3-carboxaldehyde, 6-fluoro-2-methylquinoline, 2-cyclopropyl-4-(4-fluorophenyl) quinoline-3-carboxaldehyde or 8-fluoroquinoline and other quinoline small molecules into a mixing machine at 180℃ to prepare a eutectic with uniform composition.

[0042] In the mixing step, the mass fraction ratio of polymethyl methacrylate, styrene-methyl methacrylate copolymer or polyetherimide to N-methyl pyrrolidone solution is 30%:70%, and the mass fraction ratio of quinoline small molecules to polymethyl methacrylate or styrene-methyl methacrylate copolymer or polyetherimide or polypropylene is (0.01%-8%):(99.9-92%).

[0043] (2) Film preparation:

[0044] In the film preparation step, the mixed film is prepared by using casting or melt extrusion biaxial stretching.

[0045] ① For the mixed solution of polymethyl methacrylate, styrene-methyl methacrylate copolymer or polyetherimide:

[0046] The mixed solution is cast on a glass substrate, and then dried at 60℃ for 4 hours, and then the polymethyl methacrylate composite film and the styrene-methyl methacrylate copolymer composite film are transferred to a 150℃ oven, and the polyetherimide composite film is transferred to a 250℃ oven, and dried for 6 hours respectively to completely remove the solvent and eliminate film defects. The composite film cooled naturally is immersed in deionized water for peeling to obtain a complete quinoline small molecule modified polymethyl methacrylate blend film, a quinoline small molecule modified styrene-methyl methacrylate copolymer blend film and a quinoline small molecule modified polyetherimide blend film.

[0047] ② For the eutectic of quinoline small molecules and polypropylene:

[0048] The eutectic of polypropylene and quinoline small molecules is cooled, granulated, extruded and formed, and then bidirectional stretched to prepare a quinoline small molecule modified bidirectional stretched polypropylene film.

[0049] The quinoline small molecule provided by the application includes but is not limited to the structural formula as shown below:

[0050]

[0051] wherein R1 and R2, R3 are each independently selected from any one of H, -OH, -F, -NO2 and the like;

[0052] R4 is selected from any one of H, -OH, -CH3, -CH2CH3, and the like;

[0053] R5 is selected from any one of H, -F, -OH, and the like;

[0054] R6 is selected from H, -OH or -CHO and the like.

[0055] The quinoline small molecule is in an electron-deficient state due to the intramolecular carbon-nitrogen double bond structure of the quinoline skeleton itself, and has a very high electron affinity. Compared with the polymer matrix, the quinoline small molecule has a lower LUMO energy level, so it has a strong electron affinity, which makes it easier to capture free charges from the polymer matrix. Secondly, compared with fullerene, perylene tetracarboxylic diimide, indenocarbazole dithiophene and the like with a large conjugated system, the quinoline small molecule has a large band gap (4.3eV) to meet the insulation requirements of the polymer dielectric. By introducing aldehyde groups, ester groups, hydroxyl groups, F atoms, nitro groups and the like, the electron-withdrawing ability and free radical capturing ability of the quinoline small molecule can be controlled.

[0056] From the aspects of reducing leakage current and improving breakdown field strength, the quinoline small molecule with high electron affinity is introduced to blend modify the linear polymer dielectric (such as polymethyl methacrylate, styrene-methyl methacrylate copolymer, polyetherimide and polypropylene) to construct the charge trap in the polymer matrix by using the strong electron affinity of the quinoline small molecule, so as to reduce the leakage current and improve the breakdown field strength of the polymer dielectric, thereby greatly improving the energy storage density of the polymer dielectric.

[0057] In terms of inhibiting the conductance loss, under high electric field, there is a certain electrode charge injection and dielectric internal ionization. These carriers in the polymer dielectric will cause the leakage current in the material to increase sharply under high electric field, and then a large amount of Joule heat is accumulated, finally leading to the breakdown of the polymer dielectric. However, through the trap effect of the electron-deficient quinoline small molecule introduced in the polymer dielectric, the carriers will be slowed down or captured by the trap, at the same time, the carriers will be collided and scattered by defects or phonons. Finally, the organic trap will cause the energy of the secondary impact ionization electron to be insufficient, thereby reducing the leakage current and improving the breakdown field strength.

[0058] In terms of improving the breakdown field strength, the quinoline small molecule can capture high-energy electrons, and itself is decomposed, excited and ionized to form free radicals, so as to weaken the impact of electrons on the polymer molecular chain under strong electric field, thereby improving the breakdown field strength of the polymer material.

[0059] In summary, the quinoline small molecule provided in the application has two main effects in the polymer dielectric matrix: (1) the capture effect of the charge trap on the free electron, and (2) the transition of the charge from the HOMO level to the LUMO level of the quinoline small molecule. The capture effect of the free electron mainly comes from the high electron affinity of the quinoline ring, and the electron conduction depends on the band gap width and the blending content of the organic semiconductor. Under very low copolymerization content, the quinoline organic small molecule can capture most of the carriers in the polymer, and as the content of the quinoline small molecule in the polymer matrix increases, the capture site density increases and the leakage current density decreases. When the content of the quinoline small molecule is further increased, the space distance between the conjugated quinoline rings becomes smaller and smaller, which will lead to the formation of π-π stacking, the excitation charge jumps from the HOMO level to the LUMO level, and finally the insulation of the polymer dielectric is destroyed. Therefore, the blending content of the quinoline small molecule is crucial for capturing the free carrier while maintaining high insulation performance.

[0060] (3) Dielectric energy storage performance of the polymer composite film modified by the quinoline small molecule blending:

[0061] ① Dielectric energy storage performance of the polymethyl methacrylate modified by 8-hydroxyquinoline blending

[0062] The Weibull distribution of the breakdown field strength of 8-hydroxyquinoline blend-modified polymethyl methacrylate is as follows: Figure 4 As shown, its optimal characteristic breakdown field strength is approximately 745 MV / m, which is 44% higher than that of pure polymethyl methacrylate (516 MV / m).

[0063] The discharge efficiency and energy density of 8-hydroxyquinoline blend-modified polymethyl methacrylate as a function of electric field strength are as follows: Figure 5 As shown, under an electric field of 750 MV / m, the discharge efficiency is 89% and the discharge energy density is 14.1 J / cm². -3 .

[0064] ② Dielectric energy storage performance of quinoline-3-formaldehyde blend-modified styrene-methyl methacrylate copolymer

[0065] The Weibull distribution of the breakdown field strength of quinoline-3-formaldehyde blend-modified styrene-methyl methacrylate copolymer is as follows: Figure 6 As shown, its characteristic breakdown field strength is approximately 702 MV / m, which is nearly 44% higher than that of pure styrene-methyl methacrylate copolymer (489 MV / m).

[0066] The discharge efficiency and energy density of quinoline-3-carboxaldehyde blend-modified styrene-methyl methacrylate copolymer as a function of electric field strength are as follows: Figure 7 As shown, under an electric field of 700 MV / m, the discharge efficiency is 89% and the discharge energy density is 12.39 J / cm². -3 .

[0067] ③ Dielectric energy storage performance of polyetherimide modified with 6-fluoro-2-methylquinoline blend

[0068] The Weibull distribution of the breakdown field strength of 6-fluoro-2-methylquinoline blend-modified polyetherimide is as follows: Figure 8 As shown, its characteristic breakdown field strength is approximately 577 MV / m, which is 63% higher than that of pure polyetherimide (355 MV / m).

[0069] The discharge efficiency and energy density of 6-fluoro-2-methylquinoline blend-modified polyetherimide as a function of electric field strength are shown in the figure below. Figure 9 As shown. Under an electric field of 600 MV / m, the discharge efficiency is 90%, and the discharge energy density is 8 J / cm². -3 .

[0070] ④ Dielectric energy storage performance of 8-fluoroquinoline blend-modified polypropylene. The Weibull distribution of the breakdown field strength of the 8-fluoroquinoline blend-modified polypropylene material is shown in the figure. Figure 10As shown, the characteristic breakdown field strength is about 725 MV / m, which is 12% higher than that of pure polypropylene (646 MV / m).

[0071] The discharge efficiency and energy density of the 8-fluoroquinoline blended modified polypropylene material as a function of electric field strength are shown in Figure 11 At an electric field of 450 MV / m, the discharge efficiency is 88% and the discharge energy density is 4 J / cm -3 .

[0072] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0073] It is to be understood that the application is not limited to the precise details of design and construction shown above and illustrated in the drawings, but that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The scope of the application is limited only by the claims appended hereto.

Claims

1. A method for preparing a quinoline-based small molecule blend modified polymer dielectric material, characterized in that, Includes the following steps: (1) Preparation of blend solution by blending: Styrene-methyl methacrylate copolymer or polyetherimide is added to N-methylpyrrolidone solution, and quinoline small molecules are added to obtain a blend solution; (2) Preparation of thin films: The blend solution is cast onto a substrate, pre-dried at a temperature below 100°C, then heated and dried, naturally cooled, and then soaked in water for peeling to prepare a composite wet film. The quinoline-type small molecule has the following structural formula: Among them, R1, R2, and R3 are each independently selected from any one of H, -OH, -F, and -NO2; R4 is selected from H, -OH, -CH3, -CH2CH3. Any one of them; R5 is selected from H, -F, -OH, Any one of them; R6 is selected from H, -OH, or -CHO.

2. The method for preparing quinoline-based small molecule blended modified polymer dielectric materials according to claim 1, characterized in that, In step (1), the mass fraction ratio of the quinoline small molecule to the styrene-methyl methacrylate copolymer or the polyetherimide is (0.01% to 8%): (99.9% to 92%).

3. The method for preparing quinoline-based small molecule blended modified polymer dielectric materials according to claim 1, characterized in that, In step (1), the mass fraction ratio of the styrene-methyl methacrylate copolymer or the polyetherimide to the N-methylpyrrolidone solution is (20% to 40%): (80% to 60%).

4. The method for preparing quinoline-based small molecule blended modified polymer dielectric materials according to claim 1, characterized in that, In step (2), the initial drying temperature is 50-70°C and the initial drying time is 4 hours.

5. The method for preparing quinoline-based small molecule blended modified polymer dielectric materials according to claim 1, characterized in that, In step (2), the heating and drying time is 6 hours; the heating and drying temperature of the styrene-methyl methacrylate copolymer blend solution is 130-160°C; and the heating and drying temperature of the polyetherimide blend solution is 230-260°C.

6. The quinoline-based small molecule blended modified polymer dielectric material prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the quinoline-based small molecule blended modified polymer dielectric material prepared by the preparation method according to any one of claims 1 to 5 in dielectric capacitors.

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